1. Field of the Invention
The present invention pertains to methods for non-specifically enhancing the immune system response of a subject. In one embodiment, the immune response is enhanced in conjunction with the artificial contact of the immune system of the subject with an antigen. In another embodiment, the vigor of a weak but existing immune response is enhanced. Specifically, the method comprises withdrawing leukocytes from a subject, physically altering the withdrawn leukocytes, and returning the altered leukocytes to the subject to enhance the immune response.
2. Description of the Prior Art
Immune system responses may be classified as humoral responses or cell-mediated responses. A humoral response is a response which is mediated by B lymphocytes in the form of freely diffusible antibody molecules. A cell-mediated response is a response mediated by specifically reactive lymphocytes, such as T lymphocytes or T cells, rather than antibodies.
Basic differences exist between humoral responses and cell-mediated responses. The time period from exposure to an antigen until elicitation of an immune reaction is minutes to hours for a humoral response and one or more days for a cell-mediated response. Humoral antibodies are generally specific for small antigenic determinants.
T lymphocytes are generally specific for antigens associated with specific molecules on cell surfaces.
Millions of distinct T cell clones exist in a particular person. Each clone is characterized by the proteins (the T cell receptor) carried on the surface of the T cell. The interaction of a receptor with a particular antigen requires that the receptor have a receptor site which is geometrically and chemically receptive to a corresponding site on the antigen. The forces which bind a receptor to an antigen consist of attractive forces which include hydrogen bonding, nonpolar bonding, ionic interactions, and Van der Waal's forces. The strength of these forces is inversely proportional to the distance between the interacting groups. Any structural variations in the geometry of the antigen can inhibit or prevent the binding of the receptor to the antigen. Once a receptor binds to an antigen on a cell, the cell may become activated, produce immunologically important molecules, divide to form many identical cell copies, and generally produce a strong and specific immunological reaction.
T cell reactions or cell-mediated responses are generally a beneficial defense of the body. A deficiency in the immune system response (immunodeficiency disease) leads to attack by pathogens, viruses, bacteria and fungi or cancer. Certain cell-mediated responses, however, are harmful because they cause tissue destruction. Examples of such harmful immune responses are hypersensitivity reactions (delayed-type and immediate), rejections of allografts, graft-versus-host reactions, and some allergic reactions. In addition, some autoimmune diseases are also harmful, such as myasthenia gravis, rheumatoid arthritis, systemic lupus erythematosus, multiple sclerosis, some forms of diabetes mellitus, thyroiditis, anterior uveitis, and Grave's disease.
One such harmful cell-mediated response is the rejection of allografts. An allograft (allogeneic graft, homograft) is a graft of a cell, tissue or organ which is transferred from a donor to a recipient of the same species but of disparate genotype. Because of extensive polymorphism of certain surface glycoproteins (glycoproteins existing in different forms at different stages of development), the grafted cells almost always have on their surfaces histocompatibility or transplantation antigens that are lacking on host cells and vice versa. The host responds by rejecting the allograft through a cell-mediated response.
A graft-versus-host reaction (GVH) occurs when lymphocytes are transferred from an immunologically competent donor (e.g., normal adult) to an allogeneic incompetent recipient (e.g., newborn). Ordinarily an immunologically competent host will destroy an allograft through a cell-mediated response. However an incompetent host cannot reject such a graft and the graft instead rejects the host. These reactions have clinical importance when normal thymus or bone marrow cells are transferred to immunodeficient humans (e.g., infants with genetic defects, subjects with leukemia treated with cytotoxic drugs and/or whole-body x-irradiation).
In autoimmune diseases, the immune system fails to recognize certain cells or parts of cells as its own ("self"). Autoimmunity is characterized by a specific humoral or cell-mediated response against the constituents of the body's own tissues (autoantigens) resulting in tissue destruction. This autoimmune response is characterized by the production of autoantibodies and autoreactive T cells.
Allergies are a hypersensitive state caused by exposure of the immune system to a particular allergen, and re-exposure, which causes an altered capacity to react. Allergic responses may be immediate or delayed. In some allergic responses, the immune system responds to a normally harmless substance, such as pollen, animal dander, or dust. In these allergic responses, sensitized T lymphocytes react with an allergen or antigen and release lymphokines which produce inflammation. Disease results from the inflammatory reaction caused by these environmental antigens. An example of such an allergic reaction is allergic contact dermatitis.
U.S. Pat. Nos. 4,321,919, 4,398,906, 4,428,744, and 4,464,166, all issued to Edelson, the contents of which are incorporated herein by reference, describe methods for specifically reducing the functioning lymphocyte population of a human subject. The Edelson references describe methods for treating the blood of a diseased subject wherein the disease-producing blood cells have been naturally stimulated as a consequence of the disease state. Specifically, the methods involve treating such naturally stimulated specific human blood cells, such as lymphocytes, with a dissolved photoactivatable drug, such as a psoralen, which is capable of forming photoadducts with the DNA in the cells in the presence of ultraviolet radiation. The lymphocytes and photoactivatable drug are then treated extracorporeally with ultraviolet radiation thereby modifying the lymphocytes. Following extracorporeal irradiation, the modified specific lymphocytes are returned to the subject. The modified specific lymphocytes are cleared from the subject's system by natural processes, but at an accelerated pace, presumably because of disruption of cell membrane integrity, alteration of the DNA within the cells, or similar conditions, often associated with substantial loss of cellular effectiveness or viability.
European Patent Application publication number 284,409, published Sep. 28, 1988, (U.S. Pat. No. 4,838,852), issued to Edelson et al., the contents of which are incorporated herein by reference, describes a method for specifically altering the immune system response of a subject to a specific antigen. Specifically, the Edelson et al. method comprises the steps of (a) contacting the subject's immune system with the specific antigen for a suitable time to artificially stimulate the immune system, (b) withdrawing blood cell containing material, including antigen stimulated blood cell material, from the subject, (c) treating the withdrawn material or cells so as to alter the specifically stimulated cells, and (d) returning the treated material or cells to the subject. Edelson et al. states that it may be possible to alter the cells and render them incapable of recognizing an antigen by first withdrawing blood cell containing material from the subject, treating the withdrawn material to alter the cells, returning the treated material to the subject and then contacting the subject's immune system with a specific antigen.
European Patent Application publication no. 333,606c, published Sep. 20, 1989, discloses a method for treating an autoimmune disease which comprises activating T lymphocyte cells specific for the autoimmune disease by the steps of exposing the T cells to an antigen specific for the autoimmune disease and treating the cells with a photoreactive psoralen cross-linking agent selective for the receptor on the cell membrane followed by photoactivation.
Specific immune unresponsiveness has been reported to be induced in vivo in rodents by immunizing the animal with autologous antigen-specific lymphoblasts obtained after in vitro sensitization, fractionation, and emulsification in Freund's complete adjuvant, L. C. Andersson et al., Nature, 264, pp. 778-780 (1976). Use of the nonspecific adjuvant to stimulate the specific response was necessary in that study.
Pretreatment of effector cells with 8-methoxypsoralen and ultraviolet A light has been reported to render the specific effector cells of graft rejection immunogenic for the syngeneic recipient, M. Perez et al., The Journal of Investigative Dermatology, 92, pp. 669-676 (1989). Reinfusion of photodamaged cells results in an immunosuppressive host response that permits prolonged retention of histoincompatible skin grafts and specifically inhibits in vitro and in vivo responses that correlate with allograft rejection.
Thus, a variety of methods are known to disable specific lymphocytes in diseased subjects, to attenuate specific lymphocytes to create vaccines, and to disable specific artificially-stimulated lymphocytes in healthy subjects to prevent disease. There is still a need, however, for a method to non-specifically enhance the immune system response of a subject. Such a method would permit the stimulation of a competent or incompetent immune system prior to an anticipated natural or artificial contact with an antigen, would permit the stimulation of an immune system in a subject already naturally but weakly stimulated with an antigen such as those associated with immunodeficiency disease and chronic infections, and would permit the stimulation of an immune system in a subject about to receive a vaccine. Also, immunoregulatory T cells capable of inhibiting undesirable immunologic reactions such as those found in autoimmune diseases or graft rejections could also be stimulated and weak anti-tumor responses could be enhanced. The present invention provides such a method for non-specifically enhancing the immune system response of a subject optionally with or without artificially contacting the subject's immune system with an antigen. The present invention also provides a method for preparing an autologous non-specific leukocyte adjuvant.